The invention relates to a valve, in particular for compressors, comprising a valve seat, which has at least one annular passage channel for the controlled medium, a catcher, which is arranged at a distance above the valve seat, and at least one sealing element, which can be moved between the valve seat and the catcher in order to carry out the lifting movement and controls one or several passage channels each of the valve seat, where each passage is assigned a sealing ring, which projects into the passage channel with one part of its profile when the valve is closed and abuts the sealing surfaces, which extend into the valve seat and/or the sealing rings at oblique angles to the direction of the lifting movement of the sealing rings.
Sealing valves of this design have been known for a long time. DE-PS 202 609 of 1908 describes and presents (FIG. 6) a valve, whose sealing surfaces extend conically into the valve seat and are sealed by the conical valve rings, which project partially into the passage channels. Later trough-shaped or bowl-shaped hollow bodies made of metal were used as the sealing elements of valves. DE-OS 24 46 977 discloses ring valves, whose sealing rings are designed toroidally with a circular cross section or with another flow-optimum, rounded profile, e.g. tear-shaped. Finally a valve with sealing rings that abut with a circular cross sectional profile against the tilted sealing surfaces of the valve seat is disclosed in U.S. Pat. No. 3,536,094.
These valves all have the drawback that they are actually sealed when their sealing elements fit accurately on the sealing surfaces of the passage channels of the valve seat that they control. If the valve parts are fabricated inaccurately or change their dimensions during service, e.g., through differential thermal expansion of the valve seat and the sealing rings, through swelling of valve rings made of non-metallic material during the absorption of liquid or through other affects of the medium, then the valve no longer seals completely.
If a sealing ring, for example due to thermal expansion, exhibits a somewhat greater mean diameter than the associated passage channel, it abuts only with its outer rim against the outer sealing surface of the passage channel, whereas a gap remains between the inner sealing surface and the sealing ring. There are similar drawbacks when the sealing rings, even if they are made of metal, become distorted when the valve is operating due to thermal or mechanical stresses or when the valve pieces themselves are manufactured inaccurately. The resulting leaks result not only in leak losses with a resulting decrease in the efficiency of the compressor but also they cause additional noises and thermal stresses. With sealing rings made of plastic the absorption of moisture can result in significant changes in dimensions, resulting in the same drawbacks.
An attempt to enable a tight abutting between the sealing rings and the sealing surfaces of the valve seat that are assigned to them with differential thermal expansion is known from GB-PS 2 071 818. This is to be achieved in that the sealing rings designed with a rounded off contoured profile are designed flexible and the spring force is transferred to the sealing rings, inserting spacers with rounded off surface. The rounded off spacers are to bring about that the sealing rings are bent and twisted so that they abut sealingly against the sealing surfaces of the valve seat despite the deviating shape. Apart from the fact that in this design for the sealing rings materials have to be used that are adequately flexible and, therefore, can be stressed only slightly or moderately mechanically, in most cases it is not possible to bend and twist the sealing rings to an adequate degree, for which reason leaks cannot be reliably avoided. In addition, the additionally mandatory spacers between the sealing rings and the associated springs lead to a disadvantageous increase in the cost of production, increase in mass of the moved valve parts during service and to a higher space requirement.
The object of the present invention is to avoid the cited drawbacks of the known designs and to provide a simple design to reliably prevent leaks caused by dimensional differences between the sealing rings and the associated sealing surfaces of the valve seat.